Well, it could be a lot of things, but none of them explain it. For instance, if the speed of sound is 1125 ft./sec, the wavelength of 150Hz in air is 7½ feet, so a half wavelength would be 3¾', wouldn't explain trying to match the voice coil planes. I think they are just wired wrong.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer